Prior to operation of a pump, the impeller is spaced from the pump casing by a predetermined distance, commonly referred to as the running clearance. During operation of the pump, the suction side of the pump casing assembly, as well as the adjacent face of the pump impeller, are subject to abrasive wear. As a result of this wear on the impeller face and pump casing, the running clearance becomes larger after operation of the pump. However, as the running clearance increases, increased turbulence accelerates the erosion and wear on the impeller and pump casing, and suction performance is reduced. As a result, pump performance deteriorates resulting in higher power consumption, and the accelerated wear causes the impeller and pump casing to wear out prematurely. It is therefore important to maintain the running clearance at a selected distance.
Currently available devices for adjusting the running clearance of a pump have several disadvantages. For example, some systems require the pump to be shut down and the drive gear disassembled in order to make the adjustment. Depending on the size of a pump, this procedure can take anywhere from several hours to two days, during which time the pump is off-line, resulting in a loss of production. Other adjustment devices use mechanisms whose performance will deteriorate and ultimately cease when subjected to media containing solid particles, which is a common operating condition. Other currently available adjustment devices produce a gap between the intake liner and casing while making the adjustment, resulting in the problems discussed above, namely, severe turbulence, possible cavitation, and accelerated erosion.
A need therefore exists for an improved device for adjusting the running clearance of a pump impeller. The present invention fulfills this need, and provides further related advantages.